Wells can be drilled into a surface location or subsea, ocean bed to access liquid and gaseous hydrocarbons, or other fluids, stored in subterranean formations. A well may be drilled using a drill bit attached to the end of a drill string. Example drill strings may include segments of drill pipe, drill collars, a bottomhole assembly (“BHA”), and additional components that facilitate rotation of the drill bit to remove formation materials and create a wellbore. During the drilling process, drilling fluid, commonly referred to as “drilling mud” or “mud,” can be pumped through the drill string to nozzles within the drill bit. The drilling fluid provides lubrication and cooling to the drill bit during the drilling operation, and carries drill cuttings to the surface through an annular channel between the drill string and wellbore wall.
The drilling fluid pressure may be leveraged to operate components in the BHA. For example, the BHA may include a mud motor located above the drill bit. The drilling mud provides a fluid pressure that the mud motor converts to a force usable by the drill bit or other parts of the BHA to penetrate a formation. The mud motor may be a rigid portion of the BHA and primarily responsible for generating torque for rotating the drill bit to break apart rock within the formation. The drill bit that is used may include a roller cone bit, a fixed cutter bit, or the like. An example drill bit may include a fixed cutter drill bit with polycrystalline diamond compact (“PDC”) cutters. When the drill bit is rotated, the PDC cutters can mechanically shear or break material from the surrounding formation. For a drill bit coupled to a mud motor to apply high forces, such as where very hard rocks and minerals are contained within the surrounding formation, the mud motor may be used to generate high levels of torque.
In some formations, repeated percussive forces may be effective in penetrating the surrounding rock and/or other material. The repeated percussive forces may be applied through a percussion hammer drill bit that uses linear, axial movement of the drill bit to break or otherwise remove material from a surrounding formation. The energy for the material removal is therefore produced by the impact of the total weight of the drill string and linear inertia of the percussive device, and the percussive device may not need the high levels of torque used by a rotary PDC drill bit.
Traditional methods of providing a repeated percussive force in a bottomhole assembly include an air hammer for air drilling applications, or a fluid hammer for more conventional drilling in which fluid may be used to lubricate the drill bit and provide circulation of drilling fluid through the wellbore and drill string. The use of an air hammer is largely used in applications in which drilling fluid is not used, and is therefore commonly used in more shallow wells that do not have formation fluid entering the wellbore. A fluid hammer or “mud hammer” provides a repeated percussive force using a fluid, such as the drilling fluid, to generate a hydraulic pressure to provide energy in an axial direction.